Leadframe-based packages for solid state light emitting devices having heat dissipating regions in packaging

ABSTRACT

A modular package for a light emitting device includes a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness. The leadframe further includes an electrical lead extending laterally away from the second region, and the package further includes a thermoset package body on the leadframe and surrounding the first region. The thermoset package body may be on both the top and bottom surfaces of the second region. A leak barrier may be on the leadframe, and the package body may be on the leak barrier. Methods of forming modular packages including thermoset package bodies on leadframes are also disclosed.

CLAIM OF PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 11/657,347 now U.S. Pat No. 8,044,418, filed Jan. 24, 2007which is continuation-in-part of U.S. patent application Ser. No.11/486,244 now U.S. Pat No. 7,960,819, filed on Jul. 13, 2006, thedisclosures of which are hereby incorporated by reference herein as ifset forth in their entireties.

FIELD OF THE INVENTION

This invention relates to solid state light emitting devices, and moreparticularly to packages for solid state light emitting devices andmethods of forming packages for solid state light emitting devices.

BACKGROUND

It is known to mount solid state light sources, such as semiconductorlight emitting devices, in packages that may provide protection, colorselection, focusing, and the like, for light emitted by the lightemitting device. A solid state light emitting device may be, forexample, an organic or inorganic light emitting diode (“LED”). Somepackages for light emitting diodes are described in U.S. Pre-grantPublication Nos. 2004/0079957, 2004/0126913, and 2005/0269587 which areassigned to the assignee of the present invention, and which areincorporated herein by reference as if set forth fully herein.

Packages as described in the above referenced publications may besuitable for high power, solid state illumination applications. However,notwithstanding the advances described therein, there remains a need forimproved packages in which multiple LEDs may be mounted. In particular,in some general lighting applications it may be desirable for an LEDpackage to include multiple LEDs emitting in different regions of thevisible spectrum. Light emitted by the LEDs may combine to produce adesired intensity and/or color of light, such as white light or anyother desired color. In that case, it may be desirable for the LEDs inthe package to be mounted relatively closely together.

A typical leadframe-based LED package includes electrical leads,contacts or traces for electrically connecting the LED package to anexternal circuit. In a typical LED package 10 illustrated in FIG. 1A, anLED chip 12 is mounted on a reflective cup 13 by means of a solder bondor conductive epoxy. One or more wirebonds 11 connect the ohmic contactsof the LED chip 12 to leads 15A and/or 15B, which may be attached to orintegral with the reflective cup 13. The reflective cup 13 may be filledwith an encapsulant material 16 containing a wavelength conversionmaterial such as a phosphor. Light emitted by the LED at a firstwavelength may be absorbed by the phosphor, which may responsively emitlight at a second wavelength. The entire assembly is then encapsulatedin a clear protective resin 14, which may be molded in the shape of alens to collimate the light emitted from the LED chip 12. However, heatretention may be an issue for a package such as the package 10 shown inFIG. 1A, since it may be difficult to extract heat through the leads15A, 15B, as both leads 15A, 15B cannot be connected to a heatsink, orthey will be electrically shorted. Furthermore, both leads 15A, 15B areusually made of thin sheet metal of 0.50 mm maximal thickness, beyondwhich it is difficult to be manufactured and handled.

A conventional surface-mountable leadframe-based package 20 isillustrated in FIG. 1B. The package 20 includes an LED chip 22 mountedon a reflective cup 23. One or more wirebonds 21 connect the ohmiccontacts of the LED chip 22 to leads 25A and/or 25B, which may beattached to or integral with the reflective cup 23. A clear protectiveresin 24 is cast around the assembly. The reflective cup 23 may beformed by stamping a thin sheet of metal when the leadframe is formed.Stamping the reflective cup 23 may result in thinning of the base and/orsidewalls of the cup 23, thus reducing its thermal spreading propertiesand capacity to dissipate heat generated by the semiconductor chipsmounted at the bottom of the cup. Hence, less heat is extracted out ofthe package through the leads 25A, 25B, resulting in higher thermalresistance that limits the performance of the device. This type ofpackage usually can handle a maximum power up to only about 0.5 Watt.

SUMMARY

Embodiments of the invention provide a modular package for a lightemitting device. The modular package includes a leadframe including afirst region having a top surface, a bottom surface and a firstthickness and a second region having a top surface, a bottom surface anda second thickness that is less than the first thickness. The leadframefurther includes an electrical lead extending laterally away from thesecond region, and the package further includes a thermoset package bodyon the leadframe and surrounding the first region. The thermoset packagebody may be on both the top and bottom surfaces of the second region.

The second region may include a recess in the leadframe, and thethermoset package body may at least partially fill the recess.

The first region may include a die mounting region that is isolated fromthe electrical lead, and the thermoset package body may include uppersidewalls that define an optical cavity above the die mounting region.The upper sidewalls may include oblique inner surfaces that define areflector cup surrounding the die mounting region, and the package mayfurther include an encapsulant in the reflector cup.

In some embodiments, at least a portion of the thermoset package bodymay extend through the leadframe.

The first region may include a reflector cup therein including obliquesidewalls extending from an upper corner of the reflector cup to a baseof the reflector cup. A third thickness between the base of thereflector cup and the bottom surface of the first region is greater thanthe second thickness.

A width of the first region may be greater than a width of the base ofthe reflector cup. Furthermore, a width of the first region may begreater than or equal to a width of the reflector cup at the uppercorner thereof.

The modular package may further include a submount on the base of thereflector cup, a solid state light emitting device on the submount, anda wirebond connection from the solid state light emitting device to theelectrical lead.

The thermoset package body may include upper sidewalls that define anoptical cavity above the reflector cup. In particular, the reflector cupmay include a first reflector cup and the upper sidewalls may includeoblique inner surfaces that define a second reflector cup surroundingthe first reflector cup.

The thermoset package body may have a bottom surface that issubstantially coplanar with the bottom surface of the first region.

The modular package may further include a plurality of electrical leads,and the first region may include a plurality of die mounting pads thatare electrically connected to respective ones of the plurality ofelectrical leads and that are configured to receive a light emittingdevice.

Methods of forming a package for a solid state light emitting deviceaccording to some embodiments of the invention include providing aleadframe including a first region having a top surface, a bottomsurface and a first thickness, a second region having a top surface, abottom surface and a second thickness that is less than the firstthickness, and an electrical lead extending laterally away from thesecond region. The leadframe is placed into a mold having a mold cavity,and a thermoset precursor material is dispensed into the mold cavity.Pressure is applied to the mold, and the thermoset precursor material iscured to form a thermoset package body on the leadframe.

The thermoset package body may expose the bottom surface of the firstregion, and the thermoset package body may be at least partially formedbeneath a bottom surface of the electrical lead.

The first region may include a die mounting region, and the thermosetpackage body may include upper sidewalls that define an optical cavityabove the die mounting region and that include oblique inner surfacesthat define a reflector cup surrounding the die mounting region, themethod may further include dispensing an encapsulant in the reflectorcup.

The thermoset package body may further include a circumferential rimsurrounding the first region, and positioning the lens above thereflector cup may include bringing the lens into contact with thecircumferential rim.

The first region may include a reflector cup therein including obliquesidewalls extending from an upper corner of the reflector cup to a baseof the reflector cup. A third thickness between the base of thereflector cup and the bottom surface of the first region may be greaterthan the second thickness. The methods may further include positioning asubmount on the base of the reflector cup, positioning a solid statelight emitting device on the submount, and forming a wirebond connectionfrom the solid state light emitting device to the electrical lead.

Forming the thermoset package body may include forming the thermosetpackage body to expose a bottom surface of the first region of theleadframe.

In some embodiments, providing the leadframe may include providing aleadframe blank having a top surface, a first region having a bottomsurface and having a first thickness between the top surface of theleadframe blank and the bottom surface of the first region, and aportion extending laterally away from the first region, the portionextending laterally away from the first region having a bottom surfaceand a second thickness less than the first thickness adjacent the firstregion from the top surface of the leadframe to the bottom surface ofthe portion extending away from the first region. A reflector cup isstamped into the first region.

Stamping the reflector cup into the first region may include bringing astamp including a protrusion having a shape defining a desired shape ofthe reflector cup into contact with the upper surface of the leadframeblank above the first region, and applying sufficient energy to thestamp to impress an image of the protrusion into the first region of theleadframe blank.

The methods may further include trimming excess material squeezed outwhile stamping the reflector cup from the leadframe blank.

The reflector cup may include oblique sidewalls extending from an uppercorner of the reflector cup to a base of the reflector cup, and a thirdthickness between the base of the reflector cup and the bottom surfaceof the first region may be greater than the second thickness.

In some embodiments, providing the leadframe may include providing aleadframe blank having a top surface and a bottom surface, andselectively etching, rolling and/or milling the leadframe blank toprovide a first region having a bottom surface and having a firstthickness between the top surface of the leadframe blank and the bottomsurface of the region, and a second region having a bottom surface and asecond thickness less than the first thickness from the top surface ofthe leadframe to the bottom surface of the second region. Selectivelyetching, rolling and/or milling the leadframe blank may includeselectively etching, rolling and/or milling the leadframe blank to forma recess in the leadframe.

Some embodiments of the invention provide a modular package for a lightemitting device. The package includes a leadframe including a firstregion having a top surface, a bottom surface and a first thickness anda second region having a top surface, a bottom surface and a secondthickness that is less than the first thickness. The leadframe mayfurther include an electrical lead extending laterally away from thesecond region and a leak barrier on a surface of the first region or asurface of the second region. A package body is on the leadframe and onthe first region. The package body is on the top and bottom surfaces ofthe second region, and is also on the leak barrier.

The leak barrier may include a notch or groove in the leadframe, and thepackage body may be at least partially within the notch or groove. Insome embodiments, the leak barrier may include a protrusion on theleadframe. The package body may be on the protrusion, such that theprotrusion becomes molded inside the package body.

The package body may include a thermoset, such as a thermoset plastic.

The second region may include a recess in the leadframe, and thethermoset package body may at least partially fill the recess.

The first region may include a mounting region on the top surfacethereof. The leak barrier may be on the top surface of the first regionoutside the mounting region, and the package body may be on the leakbarrier.

The package body may include upper sidewalls that define an opticalcavity above the mounting region, and the upper sidewalls may includeoblique inner surfaces that define a reflector cup surrounding themounting region. The package may further include an encapsulant in thereflector cup.

The leadframe may include a support lead, and the leak barrier may be onthe support lead and/or on the electrical lead.

The first region may include a sidewall between the top surface and thebottom surface thereof. The leak barrier may be on the sidewall. Inparticular, the leak barrier may include a protrusion from the sidewall.

The package may further include a peripheral notch on a corner of thefirst region adjacent the bottom surface thereof. The package body mayat least partially fill the peripheral notch and expose the bottomsurface of the first region.

Methods of forming a package for a solid state light emitting deviceaccording to some embodiments of the invention include providing aleadframe including a first region having a top surface, a bottomsurface and a first thickness and a second region having a top surface,a bottom surface and a second thickness that is less than the firstthickness. The leadframe may further include an electrical leadextending laterally away from the second region and a leak barrier on asurface of the first region or the second region. The methods mayfurther include placing the leadframe into a mold having a mold cavity,dispensing a precursor material into the mold cavity, applying pressureto the mold, and curing the precursor material to form a package body onthe leadframe. The package body may be formed on the leak barrier.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate certain embodiment(s) of theinvention. In the drawings:

FIGS. 1A and 1B are cross-sectional side views illustrating conventionalpackages for light emitting devices.

FIGS. 2A is a top view and FIGS. 2B and 2C are a cross-sectional sideviews illustrating a leadframe for one or more light emitting devicesaccording to some embodiments of the present invention;

FIG. 3A is a side view and FIG. 3B is a cross sectional side view of apackage for one or more light emitting devices according to someembodiments of the invention;

FIGS. 4A and 4B are schematic diagrams illustrating the formation of alead frame according to some embodiments of the invention;

FIG. 5 is a cross sectional side view of a package for one or more lightemitting devices according to further embodiments of the invention;

FIG. 6 is a top view of a leadframe configured for use in a packageaccording to embodiments of the invention;

FIG. 7 is a cutaway view of a package for one or more light emittingdevices according to embodiments of the invention; and

FIG. 8 is a cross sectional side view of a package for one or more lightemitting devices according to still further embodiments of theinvention.

FIG. 9 is a flowchart illustrating operations according to someembodiments of the invention.

FIGS. 10A-10C are front and back isometric projections and a top view,respectively, of a dual-gauge leadframe according to some embodiments ofthe invention.

FIGS. 11A-B are front and back isometric projections of a leadframe/bodyassembly according to some embodiments of the invention.

FIG. 12 is a cross-sectional illustration of a leadframe/body assemblyaccording to some embodiments of the invention.

FIG. 13 is a detail cross-sectional illustration of an interface betweena leadframe and a package body according to some embodiments of theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the size and relative sizes of layers and regions may beexaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present. Itwill also be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “lateral” or “vertical” may be used herein to describe arelationship of one element, layer or region to another element, layeror region as illustrated in the figures. It will be understood thatthese terms are intended to encompass different orientations of thedevice in addition to the orientation depicted in the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention.The thickness of layers and regions in the drawings may be exaggeratedfor clarity. Additionally, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, embodiments of theinvention should not be construed as limited to the particular shapes ofregions illustrated herein but are to include deviations in shapes thatresult, for example, from manufacturing.

As used herein, the term semiconductor light emitting device may includea light emitting diode, laser diode and/or other semiconductor devicewhich includes one or more semiconductor layers, which may includesilicon, silicon carbide, gallium nitride and/or other semiconductormaterials, a substrate which may include sapphire, silicon, siliconcarbide and/or other microelectronic substrates, and one or more contactlayers which may include metal and/or other conductive layers. In someembodiments, ultraviolet, blue and/or green light emitting diodes(“LEDs”) may be provided. Red and/or amber LEDs may also be provided.The design and fabrication of semiconductor light emitting devices arewell known to those having skill in the art and need not be described indetail herein.

For example, the semiconductor light emitting devices packaged inaccordance with embodiments of the invention may be galliumnitride-based LEDs or lasers fabricated on a silicon carbide substratesuch as those devices manufactured and sold by Cree, Inc. of Durham,N.C. The LEDs and/or lasers may be configured to operate such that lightemission occurs through the substrate in a so-called “flip chip”orientation.

Referring now to FIGS. 2A-2C, a leadframe 100 according to someembodiments of the invention is illustrated. FIG. 2A is a top view ofthe leadframe 100, while FIGS. 2B and 2C are cross sections taken alongline A-A of FIG. 2A. The leadframe 100 includes a central region 102 anda plurality of leads 104, 106 extending away from the central region102. The electrical leads 104 196 may be electrically isolated (regioni) from one another and/or from the central region 102 of the leadframe100. The leads may be arranged such that leads of opposite polarity type(e.g. anodes or cathodes) are provided on opposite sides of theleadframe 100, which may facilitate the connection of packages using,the leadframes 100 in series.

As shown in FIGS. 2A and 2B, the leadframe 100 further has an uppersurface 100 a. The central region 102 of the leadframe 100 has asubstantially flat lower surface 102 b that is spaced apart from lowersurfaces 104 b, 104 c of the leads 104, 106 by sidewalls 102 c, Thecentral region 102 has a first thickness t₁ (i.e. the distance betweenthe upper surface 100 a of the leadframe 100 and the lower surface 102bof the central region 102), and the electrical leads 104, 106 have asecond thickness t₂ (i.e. the distance between the upper surface 100 aof the leadframe 100 and the lower surface 104 b, 106 b of therespective leads 104, 106) that is less than the first thickness t₁.

A reflector cup 120 is formed in the central region 102. The reflectorcup 124 includes an oblique sidewall that extends from the upper surface100 a of the leadframe 100 to a base 124 b located within the centralregion 102. The reflector cup 124 may have an arbitrary peripheralshape. However, in the embodiments illustrated in FIGS. 2A-2C, thereflector cup 124 has a generally circular peripheral shape. Thus, theoblique sidewall of the reflector cup 124 may form a generally circularupper lip 124 a where the reflector cup 124 intersects the upper surface100 a of the leadframe 100. The sidewall of the reflector cup 124 shownin FIGS. 2A-C has the shape of a conic section (e.g. a frustum).However, the sidewall of the reflector cup 124 may form other shapes,for example, a solid parabolic section.

The base 124 b of the reflector cup 124 has a diameter that is less thana width of the central region 102 (i.e. a distance between the sidewalls102 c of the central region 102). Furthermore, the upper lip 124 a ofthe reflector cup 124 has a diameter that may be less than or equal tothe width of the central region 102. Moreover, the thickness t₃ of thecentral region 102 between the base 124 b of the reflector cup 124 andthe lower surface 102 b of the central region 102 may be thicker thanelectrical leads 104, 106 (thickness t₂). As will be explained ingreater detail below, a package for a solid state light emitting devicemay dissipate heat through the central region 102 of the leadframe 100,rather than through the leads 104, 106. Thus, the relative physicaldimensions of the central region 102 may improve the heat dissipationproperties of the package by reducing the thermal resistance of thepackage.

In general, thermal resistance is inversely proportional to the surfacearea through which heat is conducted. That is, in a simplified model,thermal resistance is defined by the equationR _(TH) =L/kA  (1)where k is the coefficient of thermal conductivity, L is the length ofthe material through which heat is to be dissipated, and A representsthe area through which heat is to be dissipated.

In semiconductor packages, heat flows from a relatively small chip to amuch larger area of a die-attach pad. Thus, thermal spreading andconduction may not be adequately modeled by a simple one-dimensionalformula such as Equation (1). Rather, thermal resistance of a packagedevice can be more accurately modeled using a thermal spreadingresistance factor which takes into account the three-dimensionalgeometries of the chip and die-attach pad and their boundary conditions.According to this type of analysis, aside from the thermal conductivityof the die-attach pad, i.e. the heatspreader (such as the central region102 in FIGS. 2C through 3B), the surface area around and underneath thechip and its thickness are the two most important parameters to givegood thermal spreading before being conducted away through anotherinterface, such as a solder joint between the heatspreader and anexternal heatsink—which may be a metal-core PCB (Printed Circuit Board)or a housing. Hence, in the design of a dual gauge leadframe, thecentral region 102 should be large and thick enough to achieve anefficient thermal spreading, which may result in good thermalperformance for the entire package, in order to take better advantage ofthe relatively large surface area of the central region 102.

Through computer modeling, e.g. computer modeling based on Kennedy'sthermal spreading resistance graphs, it has been found that a packagehaving a low thermal resistance can be designed in a practical andcost-effective manner by having the bottom side of the semiconductorchip (which acts as a heat source) and solder pad (which acts as a heatsink) on two opposite sides of a copper substrate having a particularthickness. Thus, according to some embodiments of the invention, a dualgauge (thickness) copper alloy sheet may be provided. A thinner sectionof the sheet may be stamped into electrical leads, while the thickerportion of the sheet may be stamped to form a die attach pad on itsfront face and a solder pad on its back face. In particular embodimentsof the invention, electrical current can be adequately conducted bythinner leads, while the heat energy may be effectively spread by thethicker section in which the die-attach pad is formed and that has asurface area that is a few times that of the chip footprint. In someembodiments, the thinner section may have a thickness of about 250 μm,while the thicker section may have a thickness of about 550 μm.

Referring to FIG. 2C, a submount 116 including a plurality of solidstate light emitting devices 114 is mounted within the reflector cup 124on the base 124 b thereof. The submount 116 may include a nonconductivematerial such as aluminum nitride, silicon carbide and/or chemical vapordeposited (CVD) diamond on which a plurality of electrical traces (notshown) may be formed. The thermal conductivity of aluminum nitride andsilicon carbide is about 200 W/MK, while the thermal conductivity of CVDdiamond is about 800 W/MK. The thickness of the submount 116 may be fromabout 150 to about 400 μm, although other thicknesses may be used. Aplurality of wirebond connections 112 are made between the submount 116and the devices 114 on one hand and respective ones of the electricalleads 104, 106 on the other hand.

A package 160 including the leadframe 100 is illustrated in FIGS. 3A and3B, which are side and cross sectional side views, respectively, of apackage 160 for one or more light emitting devices. Referring to FIGS.3A and 3B, the package 160 includes a molded package body 130surrounding the leadframe 100 and a lens 140 mounted over the centralregion 102 of the leadframe 100. The electrical leads 104, 106 extendfrom region r and sides of the package body 130. Other optical features,such as reflectors, diffusers, etc., may be provided instead of or inaddition to the lens 140.

The package body 130 may be formed, for example, of thermoset and/or athermoplastic by transfer or injection molding, around the leadframe100. The thermoplastic may include a liquid crystal polymer such as aVectra® series polymers A130 and/or S135 available from TiconaEngineering Polymers. Other suitable liquid crystal polymers areavailable from Solvay Advanced Polymers. Polycarbonate, Lexan® from GEPolymers and/or PPA (polyphthalamide) from Solvay Advanced Polymers mayalso be used as the thermoplastic for the package body 130. Embodimentsincluding thermoset package bodies are described in more detail below.The package body 130 may expose the bottom surface 102 b of the centralregion 102 of the leadframe 100. The package body 130 may extend atleast partially between lower surfaces 104 b, 106 b of the leads 104,106 and a lower surface 102 b of the central region 102 of the leadframe100 while exposing at least a portion of the lower surface 102 b of thecentral region 102. Further, the package body 130 may have a bottomsurface 130 b that is coplanar with the bottom surface 102 b of thecentral region 102 of the leadframe 100. However, in some embodiments,the bottom surface 102 b of the central region 102 of the leadframe 100and the bottom surface 130 b of the package body 130 may not becoplanar. For example, the bottom surface 130 b of the package body 130may extend away from the bottom surface 102 b of the central region 102of the leadframe 100. In other embodiments, the central region 102 mayextend away from the package body 130. When the package 160 is mounted,the exposed surface 100 b of the leadframe 100 may be placed intothermal contact with, for example, an external heatsink (not shown).

As shown in FIG. 3B, the package body 130 may be formed to expose anupper surface of the central region 102 (first region of thickness t₁)of the leadframe 100 including the reflector cup 120. The package body130 may include opposing upper sidewalls 134 that define an opticalcavity 150 above the reflector cup 120 and the submount 116. The uppersidewalls 134 may include oblique inner surfaces that define a secondreflector cup 138 above and surrounding the first reflector cup 124. Thelens 140 may be positioned at least partially within the optical cavity150 above the reflector cup 120. The reflector cup 120 and the opticalcavity 150 defined by the package body 130 may be filled, for example,with a liquid encapsulant material, such as liquid silicone and/orepoxy, which may include a wavelength conversion material, such as aphosphor, therein.

The lens 140 may be positioned in contact with a circumferential rim 136that may be defined within the sidewalls 134 as shown in FIG. 3B and/ormay be a separate feature of the body 130. The circumferential rim 136may determine the vertical position of the lens 140 in relation to thesolid state light emitting devices 114 in the reflector cup 120.Furthermore, the sidewalls 134 may include a circumferential moat 132outside the circumferential rim 136. The circumferential moat 132 may beparticularly useful when a liquid encapsulant such as silicone is usedas an encapsulant for the package 160, as explained below.

In a process of assembling a package according to some embodiments ofthe invention, a liquid encapsulant is dispensed into the cavity 150defined by the package body 130. The lens 140 is then lowered into thecavity 150, where it may contact the liquid encapsulant. When the liquidencapsulant is cured, it may act as a glue to hold the lens 140 in placein the package 160. When the lens 140 is placed in contact with theliquid encapsulant, some of the encapsulant may squeeze up around thelens 140, potentially interfering with the optical/mechanical propertiesof the package 160. In embodiments of the invention including acircumferential moat 132 surrounding a circumferential rim 136, the lens140 is inserted into the cavity 150 until it contacts thecircumferential rim 136. Thus, the height of the circumferential rim 136may precisely determine the spacing between the lens 140 and the solidstate light emitting devices 114, which may improve the opticaluniformity from package to package. Excess liquid encapsulant materialmay flow preferentially into the circumferential moat 132 instead offlowing up and around the lens 140. The use of circumferential edges andmoats for control of encapsulant materials and lens placement isdescribed in detail in U.S. Pre-grant Publication No. 2005/0218421entitled “Methods For Packaging A Light Emitting Device And PackagedLight Emitting Devices”, which is assigned to the assignee of thepresent invention, the disclosure of which is incorporated herein byreference.

Formation of a leadframe 100 according to embodiments of the inventionis illustrated in FIGS. 4A and 4B. As shown therein, a leadframe blank100′ includes a central region 102′ and leads 104, 106 extending awayfrom the central region 102′. The blank may be formed, for example, ofcopper, aluminum or another metal having high thermal conductivity. Thecentral region 102′ may have a thickness of about 550 μm, while theleads 104, 106 may have a thickness of about 250 μm. The central region102′ has a thickness that is greater than the thickness of the leads104, 106. The blank 100′ is placed in a support member 320 that isshaped to receive the blank 100′. A stamp 310 including a protrusion 315is brought into contact with the blank 100′, and sufficient energy (e.g.force and/or heat) is applied to impress an image of the protrusion 315into the central region 102′. The protrusion 315 may have angledsidewalls and may have a width that is less than the width of thecentral region 102′, so that the protrusion 315 creates a reflector cup124 within the central region 102′. Excess material (not shown) that maybe squeezed out when the reflector cup 124 is formed may be trimmed offof the completed leadframe 100.

A solid state lighting package 260 according to further embodiments ofthe invention is illustrated in FIG. 5. The package 260 includes aleadframe 200 including a plurality of die mounting regions 202 locatedin a central region of the leadframe 200 and a plurality of electricalleads 204, 206 extending away from the die mounting regions. Both theupper and lower surfaces of the die mounting regions 202 are exposed. Inthe embodiments illustrated in FIG. 5, respective ones of the firstelectrical leads 206 are formed integral with corresponding ones of thedie mounting regions 202, while the second electrical leads 204 areelectrically isolated from the die mounting regions 202.

A leadframe blank 200′ is shown in top view in FIG. 6. The leadframeblank 200′ includes four die mounting regions 202 a-d that are formedintegral to four corresponding leads 206 a-d. The blank 200′ furtherincludes four electrical leads 204 a-d that are isolated from the diemounting regions 202 a-d. The die mounting regions 202 a-d and leads 204a-d and 206 a-d are held in place by an external frame 201 that may betrimmed off after a package body is molded onto the leadframe blank200′. The leadframe blank 200′ may be made of a metal having a lowthermal resistance such as copper, and may be less than about 30 milsthick. In some embodiments, the leadframe may be less than about 15 milsthick. As explained below, the leadframe 200 may be substantiallythinner than a typical leadframe, since the leadframe 200 may be mounteddirectly onto an external heatsink, so that heat is extracted from theleadframe through a large surface area opposite the surface of the diemounting region 202 a-d of the leadframe 200 on which the light emittingdevices 214 are mounted.

Returning to FIG. 5, the leadframe 200 further includes regions 224 ofreduced thickness that define recesses 226 in the leadframe 200. Thereduced thickness regions 224, 226 may be formed, for example, byselectively etching portions of the leadframe 200. A package body 230 isformed on/around the leadframe, for example by transfer or injectionmolding.

The package body 230 may expose the bottom surface 202 b of the diemounting regions 202, as well as other portions of the bottom surface ofthe leadframe 200. Further, the package body 230 may have a bottomsurface 230 b that is coplanar with the bottom surface 200 b of theleadframe 200. However, in some embodiments, the bottom surface 202 b ofthe die mounting regions 202 of the leadframe 200 and the bottom surface230 b of the package body 230 may not be coplanar. For example, thebottom surface 230 b of the package body 230 may extend beyond thebottom surface 202 b of the die mounting regions 202 of the leadframe200. In other embodiments, the die mounting regions 202 may extendbeyond the package body 230. When the package 260 is mounted, theexposed surface 200 b of the leadframe 200 may be placed into thermalcontact with, for example, an external heatsink (not shown).

The package body 230 may further be formed to fill the recesses 226defined by the reduced thickness regions 224 of the leadframe 200. Thus,the package body 230 may extend, at least partially, from a lowersurface of the reduced thickness regions 224 to a lower surface 200 b ofthe leadframe 200. By filling the recesses 226 with the package body230, the package body 230 may form a strong mechanical connection to theleadframe 200 without the necessity of an adhesive. However, an adhesiveagent may be added to the plastic used to form the package body 230 inorder to prevent or reduce an outflow of liquid encapsulant materialfrom the optical cavity 250 through seams or spaces between the plasticmaterial of the package body and the leadframe 200.

The package body 230 may be formed to expose upper surfaces of the diemounting regions 202 of the leadframe 200. The package body 230 mayinclude opposing upper sidewalls 234 that define an optical cavity 250above the die mounting regions 202. The upper sidewalls 234 may includeoblique inner surfaces 238 that define a reflector cup above andsurrounding the die mounting regions 202. A lens 240 may be positionedat least partially within the optical cavity 250 above the die mountingregions 202. The optical cavity 250 defined by the package body 230 maybe filled, for example, with a liquid encapsulant material, such asliquid silicone and/or epoxy, which may include a wavelength conversionmaterial, such as a phosphor, therein.

The lens 240 may be positioned above a circumferential rim 236 that maybe defined within the sidewalls 234 as shown in FIG. 5 and/or may be aseparate feature of the body 230. In some embodiments, such asembodiments where the body 230 is formed of a thermoset, it may bedesirable for the lens 240 not to directly contact the body 230.Furthermore, the sidewalls 234 may include a circumferential moat 232outside the circumferential rim 236. As explained above, thecircumferential moat 232 may be particularly useful when a liquidencapsulant such as silicone is used as an encapsulant for the package260 to reduce or prevent squeeze-out of the encapsulant material duringor after package assembly.

A plurality of solid state light emitting devices 214 are mounted onrespective ones of the die mounting regions 202, which are electricallyconnected to respective ones of the first electrical leads 206. Wirebondconnections 216 are made between the light emitting devices 214 andrespective ones of the second electrical leads 204.

FIG. 7 is a perspective cutaway view of a package 260 according toembodiments of the invention showing a package body 230 molded onto aleadframe 200. Four solid state light emitting devices 214 are mountedon the leadframe 200 within the optical cavity 250 defined by thesidewalls 234 of the package body 230. The solid state light emittingdevices are connected by wirebonds 216 to respective ones of the secondelectrical leads 204, which extend from a side of the package oppositethe first electrical leads 206. A lens 240 is positioned above theoptical cavity 250.

FIG. 8 is a cross sectional view of a package 360 for solid state lightemitting devices according to further embodiments of the invention.Features of the package 360 having the same reference numbers as thoseshown in FIG. 5 are similar to the corresponding features of the package260 shown in FIG. 5. In the package 360, instead of providing a separatelens element that is inserted into the package, a lens 340 is formed bydispensing a liquid encapsulant material into the cavity formed by thesidewalls 230 and curing the liquid encapsulant. Dispensed lenses arediscussed in U.S. patent application Ser. No. 11/197,096 entitled“Packages for Semiconductor Light Emitting Devices Utilizing DispensedEncapsulants and Methods of Packaging the Same ” filed Aug. 4, 2005,which is assigned to the assignee of the present invention, and thedisclosure of which is incorporated herein by reference.

In particular, after the light emitting devices 214 have been mounted onthe die attach regions 202, a first dispense of encapsulant material 330may be performed to cover the devices 214. The material of the firstdispense may include a wavelength conversion material such as aphosphor. The first encapsulant material 330 may form a convex, flat, orconcave meniscus defined by the circumferential rim 236 of the sidewallportions 234, which may be provided with sharp edge to facilitate theformation of the meniscus. After the encapsulant material 330 has beenat least partially cured, a second dispense of encapsulant material 335may be performed. The second encapsulant material 335 may be formed tohave a concave, flat, or convex meniscus defined by an upper edge 344 ofthe sidewall portions 234 depending on the amount of material dispensed.The second encapsulant material 335 may then be cured to form a lens 340above the optical cavity 250.

Embodiments of the invention may permit the formation of packages forsolid state light emitting devices in which multiple high-power devicesare arranged in close proximity, which results in a higher opticalquality emission with better color mixing. Furthermore, assembly of apackage according to embodiments of the invention may be simplified,since the package body may be formed through injection moldingtechniques.

According to some embodiments of the invention, a leadframe-basedpackage for one or more solid state light emitting devices may provide ashort thermal path between the solid state light emitting devices and anexternal heatsink, since the light emitting devices are mounted on oneside of the heatsink, while the opposite side of the leadframe is usedto contact an external heatsink. Furthermore, the surface area of theleadframe through which heat is extracted may be larger than the diemounting area, which may improve heat extraction.

As described above, the use of injection-molded thermal plastics to forma body on a leadframe may offer a low-cost solution for LED packages forgeneral-purpose device packages. However injection molded plastics maynot be suitable for all purposes. For example, injection molded plasticsmay not be suitable for packages requiring more robust thermalperformance and/or more environmental protection to the semiconductorchips packaged inside.

Accordingly, some embodiments of the invention provide a high powersemiconductor package including a more robust, high thermal-performancecomposite substrate that includes a body formed of a thermoset on adual-gauge metal leadframe. The use of a thermoset with a dual-gaugelead frame may provide particular advantages, since a thermoset may beable to fill corners and/or recesses in the leadframe where thethickness of the leadframe changes, and that may otherwise provide anundesired pathway for liquids and/or gases to pass into/out of thepackage. A package body formed using a thermoset may form a strongmechanical connection to the leadframe due in part to the dual gaugenature of the leadframe and may also form a tight seal on the leadframethat may reduce and/or prevent the flow of liquids/gases into and/or outof the package notwithstanding the dual-gauge nature of the leadframe.Thus, a package including a thermoset body on a dual gauge leadframe maybe mechanically stable and/or may have a high degree of hermeticity. Thethermoset may include a thermosettable polymer, copolymer, oligomer,and/or elastomer (or plastic), or mixtures thereof.

Accordingly, a package according to some embodiments of the inventionmay provide a multiple chip, high performance hybrid LED package that iscompatible with high solder reflow eutectic die-attach processes.Further embodiments of the invention provide a robust, high thermaldevice package that can withstand severe environmental operatingconditions at high operating power without undue distortion, bodydamage, leakage and/or failure.

A thermoset that may be used according to some embodiments of theinvention may include an epoxy, polyimide, a phenolic resin and/or anyother thermosettable material. A thermoset for use in some embodimentsof the invention can be transfer molded onto a leadframe, such as astamped or etched dual-gauge leadframe. Other types of molding may beused to form a body on a leadframe, such as injection molding and/orcasting.

When the thermoset is chemically cross-linked (i.e., cured), it willchemically bond to the leadframe to form a robust 3-dimensional solidthermoset body. The body/leadframe combination may be formed to includeone or more functional features, such as metal die bond pads, a heatsinkand electrical leads, plastic cavity, lens retention features, etc., asdescribed above in connection with FIG. 5, for example.

Although, as described above, a thermal plastic such as LCP (liquidcrystal polymer) may be used to form a molded body, a thermoset body mayoffer enhanced structural and/or environmental protection to thedevice(s) mounted in the package.

In particular, the use of a thermoset in combination with a dual-gaugeleadframe as described above may be capable of unexpectedly improvedperformance. As noted above, a dual-gauge leadframe, such as theleadframe 100 shown in FIGS. 3A and 3B and/or the leadframe 200 shown inFIG. 5, may be made, for example, by milling, stamping, and/or orrolling a metal strip to form a leadframe having areas of differentcross-sectional thickness. Different functional areas of the leadframe,such as leads, heatsinks, die attach pads, etc., can then be made and/orstamped at different sections of the leadframe to provide desiredfunctionality and/or performance.

Thermoset materials, such as thermosetting plastics are polymermaterials that may be dispensed in precursor form, such as a resin, andthen cured to a stronger form through the addition of energy, such asheat (generally near 200° C.) or irradiation. The curing processtransforms the resin into a solid plastic by a cross-linking process inwhich the molecular chains of the material react at chemically activesites and link into a rigid, three-dimensional structure. Thecross-linking process forms a molecule with a larger molecular weight,resulting in a material with a higher melting point or that simplychanges to carbon and residue without melting. Thus, a thermosetmaterial may not be melted and re-shaped after it is cured. As a resultof the formation of a three-dimensional network of bonds during thecross-linking phase, thermoset materials are generally stronger thanthermoplastic materials. Thus, thermoset materials may be better suitedfor high-temperature applications than thermoplastic materials.

Most thermosets, such as epoxy and/or polyimide, will bond to organicand/or inorganic surfaces when they come into contact with the surfaceduring the cross-linking (curing) phase. This bond at the surface may bevery strong and/or may be impervious to fluids or gases, such that asoft-gel encapsulant surrounding the semiconductor device(s) mounted inthe package may not leak out. Furthermore, the bond between thethermoset and the leadframe may reduce or prevent the entry of moistureinto the package, which could otherwise cause device failure.

In contrast, in a package including a thermoplastic molded body, theremay be no bonding between the plastic body and the leadframe on which itis molded. As such, fluids and/or gases can pass in both directionsthrough the interface between the thermoplastic and the leadframe.Accordingly, an advantage of using thermosets such as epoxy or phenolicresin may be found in the bonding and sealing properties of thermosetsat the interface with an organic and/or inorganic surface on which it ismolded. This bonding may reduce and/or prevent moisture and/or otherfluids or gases from passing through the interface. Thus, a thermosetmay provide a higher degree of hermeticity at the interface than athermal plastic can offer.

Many thermosets can withstand temperatures in excess of 350° C. withoutbecoming deformed or distorted. In general, thermosets may be able towithstand higher temperatures than conventional thermoplastic materials,such as PPA (e.g., Amodel®) and/or LCP (e.g., Vectra®), each of whichcan only withstand temperatures up to about 280° C. Accordingly, mostthermal plastic materials cannot withstand the high solder reflowtemperatures typically used for surface mount technology, which may beused to mount some LED packages.

Thermosets, such as many epoxies, can be molded by transfer molding,compression molding and/or casting processes to create plastic bodieshaving very fine details and/or intricate designs. During themolding/casting process, a thermoset may typically first transform intoa flowable state before it is cured into a solid state. During thisfluid state, high pressure can be applied to the material to allow thefluidic resin to fill even very small crevices in a mold. A thermalplastic may not be able to fill spaces as small as a thermoset can,because the injection mold for a thermal plastic is typically set at atemperature below the melting temperature of the thermal plastic, whichmay start to cool the thermal plastic to a solid state as soon as itenters the mold cavity.

Accordingly, the use of a thermoset with a dual-gauge lead frame mayprovide particular advantages, since a thermoset may be able to fillcorners and/or recesses in the leadframe where the thickness of theleadframe changes. As noted above in connection with FIG. 5, by fillingrecesses in the leadframe, such as the recesses 226, with the packagebody 230, the package body 230 may form a strong mechanical connectionto the leadframe 200 without the necessity of an adhesive. By using athermoset, the package body may form a strong mechanical connection tothe leadframe and may also form a tight seal on the leadframe that mayreduce and/or prevent the flow of liquids/gases into and/or out of thepackage. Thus, as noted above, a package including a thermoset body on adual gauge leadframe may be mechanically stable and/or may have a highdegree of hermeticity.

Although the cost of forming a leadframe body using a transfer moldedthermoset may be more expensive than using thermal plastic, the overallincrease in packaging cost may be negligible. Furthermore, inapplications desiring higher thermal performance, package quality and/orreliability, the use of thermosets may be economically justified.

FIG. 9 is a flowchart illustrating operations 900 according to someembodiments of the invention. As shown therein, a dual-gauge leadframeis provided (Block 910). The dual-gauge leadframe may be formed, forexample, by milling, etching, rolling, and/or stamping a metal blank, asdescribed above, so that the leadframe has recessed portions and/orthicker portions therein.

The dual-gauge leadframe is then placed into a mold cavity (Block 920)that has the shape of a plastic body to be molded onto the leadframe.

Examples of thermoset materials are epoxy resins and phenol-novolacresins from Nitto Denko. Such materials may be loaded with fillerparticles, such as spherical fused silica and/or irregularly-shaped TiO₂(titanium dioxide) solid particles, and/or carbon fibers atpredetermined percentage by weight in order to obtain desired physicalproperties, such as coefficient of thermal expansion (CTE), flexuralmodulus, optical surface reflectance, heat deflection temperature (HDT),etc.

The thermoset resin, in solid or liquid form, is then loaded ordispensed into the mold cavity (Block 930), which is set at a hightemperature (typically at about 175° C.). Pressure (hundreds of psia) isapplied to the thermoset resin to push the resin into the runner systemof the mold. At this time, the solid resin will melt into a solution ofvery low viscosity. The liquid resin may then flow easily through themold runners into the mold cavities, filling small crevices and cornersand recesses of the dual-gauge leadframe (Block 940). The pressure onthe mold is increased to about 1,000 psia to pack the resin into thesmallest gaps in the mold.

Inside the mold cavities, the liquid thermoset is continuously subjectedto the high mold temperature of about 175° C. or more and a highmaterial pressure of about 1,000 psia. Under these conditions, theliquid thermoset will solidify/cure in about 3-5 minutes (Block 950). Asnoted above, when a thermoset cures, a cross-linking process occurs inwhich its constituent monomers or polymers chemically react with oneanother to form large, three-dimensional molecules that give solidthermoset material rigidity and a high melting point. The cross-linkingaction also causes the thermoset to chemically adhere or bond to thedual-gauge leadframe, imparting high mechanical stability to theresulting body/leadframe structure as well as providing a tight seal tothe leadframe. This phenomenon of bonding may be desirable for a packagefor a semiconductor light emitting diode, in that an encapsulant canthen be contained and retained inside without leaking out from thepackage.

Since the thermoset resin bonds readily to surfaces, the mold cavity maybe made of hardened mold steel and polished to a mirror finish to reducethe tendency of the hardened thermoset to bond to the mold cavity. Inaddition, strong ejectors may be used to eject the molded parts from themold cavity.

FIGS. 10-13 illustrate LED packages that may be particularly suitablefor use with a thermoset or thermal-plastic material, and that may havereduced leakage of liquid or soft gel encapsulant from the package,which may increase the reliability of the package. For example, FIGS.10A, 10B and 10C are front and back isometric projections and a topview, respectively, of a dual-gauge leadframe 400 that may beparticularly suitable for use with a package body, such as the packagebody 420 shown in isometric projection in FIGS. 11A and 11B.

In particular, referring to FIGS. 10A to 10C, the leadframe 400 includesa thicker central portion 402 which functions as a heatsink as well asproviding a mounting surface 404 on which a submount, such as thesubmount 450 shown in FIG. 12, may be mounted. A plurality of relativelythinner leads 406 extend towards the central portion 402. In particular,the central portion of the leadframe 400 may have a thickness of about0.5 mm, while the leads 406 may have a thickness of about 0.25 mm. Insome embodiments, the central portion of the leadframe 400 may have athickness of about 0.55 mm. The leadframe 400 may include, for example,copper and/or a copper alloy having a high thermal conductivity of about370-400 W/m° K.

Prior to formation of the package body, the central portion 402 and theleads 406 are held in place by a support frame 410. The leads 406 may beattached directly to the support frame 410, while the central portion402 may be attached to the support frame 401 by one or more supportleads 412. Once the package body is formed on the leadframe 400, theleads 406 and the central portion 402 may be detached from the supportframe 410.

The leadframe 400 includes additional features that may help to improvethe integrity of the final package. For example, a plurality of leakbarriers 408 may be formed on/in the mounting surface 404 of the centralregion 402 of the leadframe 400. The leak barriers 408 may includefeatures such as notches and/or grooves that may be etched and/orstamped into the leadframe 400. When the package body is formed on theleadframe, the material of the package body may flow into the leakbarriers 408 and solidify on or within the leak barriers 408 when cured.The leak barriers 408 may provide a three-dimensional surface forbonding the package body to the leadframe 400. In addition, the leakbarriers 408 may provide a longer path through which a potential leakwould have to travel, thus potentially reducing the likelihood of asubstantial leak into or out of the optical cavity of the package.(Leaks may tend to occur, for example, when soft-gel encapsulantmaterial in an LED package expands or contracts due to heating orcooling.)

The leak barriers 408 may also be formed on the leads 406 as well as onthe support leads 412, as further illustrated in FIGS. 10A to 10C.

The support leads 412 may further include breakage features 409, whichmay include deeper notches and/or grooves in the support leads 412, atwhich the support leads may be easily broken or sheared to separate thecentral portion 402 from the support frame 410. In some embodiments, thebreakage features 409 may be positioned such that they are within theperiphery of the package body, so that when the support leads 412 arebroken off, no part of the support leads 412 extends outside theperiphery of the package body.

Referring to FIGS. 11A and 11B, a package body 420 may be formed on theleadframe 400. In particular, the package body 420 may be formed toexpose at least a portion of the mounting surface 404 of the centralportion 402 of the leadframe 400.

The package body 420 may include, for example, a thermoset, such as athermoset plastic. In order to discourage leakage, it may be desirableto encapsulate as much of the leadframe 400 with thermoset as possible,leaving only adequate surface areas exposed for die attach, wirebondingand heat sink. The package body 420 may further include sidewalls 425that define an optical cavity 415 above the mounting surface 404.Further, at least a portion of each of the leads 406 is exposed withinthe cavity 415. A bottom surface 405 of the central portion 402 oppositethe mounting surface 404 is also exposed by the package body 420. Thebottom surface 405 may provide heat dissipation for the package. Thus,it may be desirable for as much of the bottom surface 405 to be exposedas possible.

FIG. 12 is a schematic cross section of a package body 420′ formed on aleadframe 400 according to embodiments of the invention. Some dimensionsand/or features of the package body 420′ and the leadframe 400 have beenexaggerated for purposes of illustration. As shown in FIG. 12, asubmount 450 is mounted on the mounting surface 404 of the centralportion of the leadframe 400. A plurality of LED chips 460 are mountedon electrical traces (not shown) on the submount 450. The submount 450may include, for example, an electrically insulating, thermallyconductive material, such as aluminum nitride.

The LED chips are connected via wirebonds 419 to electrical bondpads(not shown) on the submount 450, which are in turn connected to theleads 406 via wirebonds 417. Accordingly, the submount/LED chipassemblies may be pre-assembled and mounted as a modular unit onto theleadframe 400.

The package body 420′ includes sidewalls 425 extending above theleadframe 400 and defining an optical cavity 415 above the LED chips460. At least a portion of the sidewalls 425 are formed on surfaces ofthe leads 406 and the central portion 402 including the leak barriers408, so that the package body 420′ forms a strong mechanical connectionto the leadframe as well as a connection that may reduce or inhibitleakage into/out of the optical cavity 415, as described above.

In addition, the central portion 402 of the leadframe 400 may includeother features that may enhance the mechanical stability and/or leakresistance of the final package. For example, the central portion 402 ofthe leadframe 400 may include etched and/or stamped features onsidewalls of the central portion 402 between the mounting surface 404and the bottom surface 405 thereof, such as protrusions 418. As with theleak barriers 408, the protrusions 418 may reduce or discourage leaks byincreasing the potential path length for any leak into/out of theoptical cavity 415. The protrusions 418 may further improve themechanical connection between the package body 420′ and the leadframe400.

Further, a peripheral notch 416 may be formed in the bottom corner ofthe central portion 402 of the leadframe 400 adjacent the bottom surface405 thereof. The peripheral notch 416 may be formed, for example, bystamping. In addition, the act of stamping the peripheral notch 416 intothe central portion 402 of the leadframe 400 may have the collateraleffect of producing a beneficial protrusion 418 in the sidewall of thecentral portion 402 of the leadframe 400.

A leak barrier 408 is shown in more detail in FIG. 13, which is apartial cross section of a portion of a leadframe/body assembly. Asshown therein, the leak barrier 408 may include a notch stamped into alead 406 of the leadframe 400. The body 420 at least partially extendsinto the leak barrier 408. As noted above, thermosets can be used tofill very small spaces. Thus, it may be particularly beneficial to use athermoset material to form the package body in embodiments includingleak barriers 408, as a thermoset may effectively fill and bond to smallnotches used as leak barriers.

In order to further increase the resistance of the final package toleakage, the package body 420, 420′ may be formed of a thermoset havinga coefficient of thermal expansion that is substantially matched to thecoefficient of thermal expansion of the leadframe 400. For example, somethermoset plastics have coefficients of thermal expansion of about 17.7ppm/° C., while copper, which may be used to form the leadframe 400, mayhave a coefficient of thermal expansion of about 18 ppm/° C.

The foregoing description is illustrative of the present invention andis not to be construed as limiting thereof. Although a few exemplaryembodiments of this invention have been described, those skilled in theart will readily appreciate that many modifications are possible in theexemplary embodiments without materially departing from the novelteachings and advantages of this invention. Accordingly, all suchmodifications are intended to be included within the scope of thisinvention as defined in the claims. Therefore, it is to be understoodthat the foregoing is illustrative of the present invention and is notto be construed as limited to the specific embodiments disclosed, andthat modifications to the disclosed embodiments, as well as otherembodiments, are intended to be included within the scope of theappended claims. The invention is defined by the following claims, withequivalents of the claims to be included therein.

That which is claimed is:
 1. A modular package for a light emittingdevice, comprising: a leadframe including a first region having a topsurface, a bottom surface and a first thickness and a second regionhaving a top surface, a bottom surface and a second thickness that isless than the first thickness, the leadframe further including anelectrical lead extending laterally away from the second region, whereinthe first region comprises a reflector cup having sidewalls extendingfrom an upper corner of the reflector cup to a base of the reflectorcup, and wherein the second region extends laterally beyond a sidewallof the first region such that the second region extends beyond thesidewall on opposing sides of the first region; and a package body onthe leadframe and surrounding the first region, wherein the package bodyis on the top and bottom surfaces of the electrical lead and on thebottom surface of the second region.
 2. The modular package of claim 1,wherein the second region comprises a recess in the leadframe, whereinthe thermoset package body at least partially fills the recess.
 3. Themodular package of claim 1, wherein the first region comprises amounting region, and wherein the electrical lead is isolated from themounting region, and wherein the package body includes upper sidewallsthat define an optical cavity above the mounting region.
 4. The modularpackage of claim 3, wherein the upper sidewalls include oblique innersurfaces that define a reflector cup surrounding the mounting region,the package further comprising an encapsulant in the reflector cup. 5.The modular package of claim 1, wherein at least a portion of thepackage body extends through the leadframe.
 6. The modular package ofclaim 1, wherein a third thickness between the base of the reflector cupand the bottom surface of the first region is greater than the secondthickness.
 7. The modular package of claim 6, wherein a width of thefirst region is greater than a width of the base of the reflector cup.8. The modular package of claim 6, wherein a width of the first regionis greater than or equal to a width of the reflector cup at the uppercorner thereof.
 9. The modular package of claim 6, further comprising asubmount on the base of the reflector cup, a solid state light emittingdevice on the submount, and a wirebond connection from the solid statelight emitting device to the electrical lead.
 10. The modular package ofclaim 6, wherein the package body includes upper sidewalls that definean optical cavity above the reflector cup.
 11. The modular package ofclaim 10, wherein the reflector cup comprises a first reflector cup andwherein the upper sidewalls include oblique inner surfaces that define asecond reflector cup surrounding the first reflector cup.
 12. Themodular package of claim 11, wherein a width of a base of the secondreflector cup is greater than the width of the first reflector cup atthe upper corner thereof.
 13. The modular package of claim 1, whereinthe thermoset package body has a bottom surface that is substantiallycoplanar with the bottom surface of the first region.
 14. The modularpackage of claim 1, further comprising a plurality of electrical leads,wherein the first region comprises a plurality of mounting pads that areelectrically connected to respective ones of the plurality of electricalleads and that are configured to receive a light emitting device. 15.The modular package of claim 1, wherein the thermoset package bodycomprises a thermoset plastic.
 16. The modular package of claim 1,wherein the package body comprises a thermoset.
 17. The modular packageof claim 1, wherein the package body includes an upper sidewall thatdefines an optical cavity above the first region of the leadframe, theupper sidewall having a lowermost portion that is on the electrical leadand that is spaced apart from the leadframe.
 18. The modular package ofclaim 1, wherein the package body includes a moat in an upper surfacethereof.
 19. The modular package of claim 1, further comprising a lensmounted over the first region of the leadframe, wherein sidewalls of thepackage body extend above a bottom surface of the lens.
 20. The modularpackage of claim 1, wherein the portion of the package body that is onthe top surface of the electrical lead and the portion of the packagebody that is on the bottom surface of the electrical lead comprise thesame material.
 21. A modular package for a light emitting device,comprising: a leadframe including a first region having a top surface, abottom surface and a first thickness and a second region having a topsurface, a bottom surface and a second thickness that is less than thefirst thickness, the leadframe further including an electrical leadextending laterally away from the second region, wherein the secondregion extends laterally beyond a sidewall of the first region such thatthe second region extends beyond the sidewall on opposing sides of thefirst region; a package body on the leadframe and surrounding the firstregion, wherein the package body is on the top and bottom surfaces ofthe electrical lead and on the bottom surface of the second region; anencapsulant on the top surface of the second region, wherein theencapsulant is a different material than a material of the package body,and a lens mounted over the first region of the leadframe, wherein theencapsulant is between the lens and leadframe, and wherein sidewalls ofthe package body extend above a bottom surface of the lens.
 22. Themodular package of claim 21, wherein the package body includes an uppersidewall that defines an optical cavity above the first region of theleadframe, the upper sidewall having a lowermost portion that is on theelectrical lead and that is spaced apart from the leadframe.
 23. Themodular package of claim 21, wherein the package body includes a moat inan upper surface thereof.
 24. The modular package of claim 21, whereinthe portion of the package body that is on the top surface of theelectrical lead and the portion of the package body that is on thebottom surface of the electrical lead comprise the same material.
 25. Amodular package for a light emitting device, comprising: a leadframeincluding a first region having a top surface, a bottom surface and afirst thickness and a second region having a top surface, a bottomsurface and a second thickness that is less than the first thickness,the leadframe further including an electrical lead extending laterallyaway from the second region, wherein the second region extends laterallybeyond a sidewall of the first region such that the second regionextends beyond the sidewall on opposing sides of the first region; anisolation region between the second region and the electrical lead onthe opposing sides of the first region to electrically isolate thesecond region from the electrical lead; and a package body on theleadframe and surrounding the first region, wherein the package body ison the top and bottom surfaces of the electrical lead and on the bottomsurface of the second region.
 26. The modular package of claim 25,wherein the isolation region has the second thickness.
 27. The modularpackage of claim 26, wherein the package body is on top and bottomsurfaces of the isolation region.